The range of applications and the functionalities of liquid crystal display devices have been increasing. Particularly, display modes having wide viewing angle characteristics, such as MVA (Multi-domain Vertical Alignment) and IPS (In-Plane-Switching), have been developed, and further improvements have been made thereto.
In recent years, liquid crystal display devices of an FFS (Fringe Field Switching) mode, which has evolved from the IPS mode, have been developed. In the IPS mode or the FFS mode, an electric field is generated in an in-plane direction (or an oblique direction) by using the pixel electrode and the common electrode provided on one substrate so as to rotate liquid crystal molecules in a direction parallel to the substrate. Such a display mode is called a “transverse electric field mode (transverse electric field scheme)”.
Known among liquid crystal display devices of the transverse electric field mode are liquid crystal display devices of a dual-domain mode that form two types of liquid crystal domains within one pixel. In such a display device, two types of sub-pixel regions different from each other in terms of the electrode structure (e.g., the direction of the slit provided in the pixel electrode) are provided within one pixel, and liquid crystal molecules of different sub-pixel regions rotate in opposite directions in the presence of an applied voltage.
In a liquid crystal display device of a dual-domain mode, two types of liquid crystal domains whose directors cross each other are formed when a voltage is applied. This reduces the generation of a color shift because the retardation offset is compensated even when observed from a direction parallel to the director of one liquid crystal domain, for example.
However, with small-sized display devices used in mobile devices, or the like, the size of one pixel has decreased as the definition increases, and it is in some cases difficult to form electrode structures (e.g., a plurality of “V”-shaped electrodes/slits) for forming dual domains within one pixel.
In view of this, schemes have been proposed in which different domains are formed in two adjacent pixels, rather than within one pixel. For example, Patent Document No. 1 discloses a technique for liquid crystal display devices of the IPS mode, in which different electrode structures are provided in two adjacent pixels, thereby forming two types of domains of which the directions of liquid crystal molecule rotation are opposite from each other. In the present specification, the scheme in which two types of liquid crystal domains are formed by using two adjacent pixels may be referred to as “pseudo dual-domain”. For example, Patent Document No. 2 discloses a liquid crystal display device of the FFS mode employing a pseudo dual-domain configuration.
In a pseudo dual-domain liquid crystal display device, there are formed two types of liquid crystal domains whose director directions are different from each other between two adjacent pixels in the presence of an applied voltage (see FIG. 1(d)). Thus, as with a dual-domain mode realized with one pixel described above, it is possible to improve the viewing angle characteristics of a liquid crystal display device of a transverse electric field mode.